In prior art devices such as CT, scanning imaging of an object using x-rays has been widely used. However, the traditional x-ray imaging examines the internal structure of an object without destruction by using attenuation property of a material for x-rays, and this belongs to x-ray bright-field imaging technology.
In optical imaging field, dark-field imaging is remarkably different from bright-filed imaging. Dark-field imaging is a technology of imaging a substance using non-direct light (e.g. scattered light, diffracted light, refracted light, fluorescent light, etc.). Therein, the study of visible light and electron dark-field imaging technology started relatively early, which has been widely used in scientific research, industrial field, medical field, biological field and so on. In hard x-ray imaging field, traditional hard x-ray imaging technology performs the imaging of an object using direct x-rays, i.e. using the bright-field imaging technology. As for dark-field imaging, due to the particular optical properties of hard x-rays, the manufacture of required optical elements is very difficult, and accordingly, the hard x-rays dark-field imaging can hardly be better fulfilled all along. In the 90s of the twentieth century, as the third-generation synchronous radiation source develops and the manufacturing level of delicate hard x-ray optical elements rises, the study of hard x-ray dark-field imaging technology gains certain growth, but as compared with the hard x-ray phase contrast imaging technology rising simultaneously, the hard x-ray dark-field imaging technology has always been insufficiently noticed due to low semaphore, comparatively difficult detection, long time of imaging, etc.
However, the hard x-ray dark-field imaging technology is originally advantageous over the bright-field imaging and the phase contrast imaging in terms of capabilities for distinguishing and detecting an internal fine structure of a substance. The hard x-ray dark-field imaging technology performs the imaging of the internal structure of the substance based on a difference in scattering capability of the substance for x-rays. Since the scattering of hard x-rays is at a scale of micrometer magnitude or even nanometer magnitude, the hard x-ray dark-field imaging technology can enable viewing of an internal ultrafine structure of the substance, which is undistinguishable for hard x-ray bright-field imaging and phase contrast imaging.
In recent years, researchers propose applying the hard x-ray dark-field imaging technology based on crystal used for synchronous radiation sources to cartilage tissue diagnosis and early breast cancer diagnostic imaging, and this achieves an image effect superior to the hard x-ray bright-field imaging. However, since the synchronous radiation device has a large volume, costs much and enables a small field of view, it confines the hard x-ray dark-field imaging technology to great extent in terms of applications in medical clinics and industrial detection.
Grating imaging technology was born in 2006, releasing the hard x-ray dark-field imaging from restraint by and dependence on the synchronous radiation source. With an all-purpose x-ray apparatus, it enables a hard x-ray dark-field imaging with a large field of view, and this largely reduces the difficulty facing the application of the hard x-ray dark-field imaging technology. At the beginning of 2008, Pfeiffer, et al. from Switzerland realized a hard x-ray dark-field imaging with a large field of view (e.g. 64 mm×64 mm) by use of gratings based on a Talbot-Lau interferometry method on an all-purpose x-ray apparatus. Such a grating-type hard x-ray dark-field imaging technology is capable of well distinguishing between plastic and rubber materials and of enabling view of bones in chicken wings and ultrafine structures in muscle tissues. Starting from 2006, Huang Zhifeng, et al. from Tsinghua University have conducted related studies on grating-type hard x-ray phase contrast imaging technology based on an all-purpose x-ray apparatus, and proposed a grating phase contrast imaging method based on projection in incoherent condition in the Chinese patent application No. 200810166472.9, filed in 2008 and titled “X-ray Grating Phase Contrast Imaging System and Method”, establishing an experimental platform for grating phase contrast imaging based on an all-purpose x-ray apparatus. All contents of the patent application are introduced into the present application by reference.